The long range objectives are to clarify the nature of abnormal perceptual and electrophysiologic asymmetries in affective disorders, and to assess the value of brain asymmetry measures for predicting outcome of antidepressant treatment. Specific aims are: 1) to evaluate a three-factor model in which symptoms of general negative affect, anxious arousal and anhedonia are hypothesized to be related to specific regional brain asymmetries; 2) to compare asymmetries of patients having a depressive disorder alone, an anxiety disorder alone, or both disorders; 3) to test the prediction that anxious arousal is associated with right parietotemporal activation; 4) to evaluate predicted differences in regional brain asymmetries between anhedonic and nonanhedonic subgroups of depression; 5) to test a large sample of patients on electrophysiologic measures so as to evaluate predicted differences in hemispheric asymmetries between treatment responsive and nonresponsive subgroups. A total of 200 unmedicated patients and 40 normal controls will be tested on a battery of behavioral laterality, resting electroencephalography (EEG), and cognitive event-related potential (ERP) measures in three studies. Study 1 uses a 2 X 2 design to compare patients having a MDD only, an anxiety disorder only (panic or social phobia) or both disorders, and normal controls. Subjects are also tested on electrodermal and psychometric measures of anxious arousal. Study 2 compares subgroups of anhedonic and nonanhedonic depression formed on the basis of self-reports, structured assessments of responses to pleasurable stimuli, and "interview-based" diagnoses. Study 3 compares antidepressant responders and nonresponders on the behavioral and electrophysiologic tests, as well as on the assessments of anhedonia. These studies should contribute to the identification of subtypes of depression and characteristic regional brain asymmetries and distinctive clinical features.